【作者】 阮秀秀；

【导师】 朱利中； 陈宝梁；

【作者基本信息】 浙江大学 ， 环境科学， 2008， 博士

【摘要】 有机膨润土吸附性能良好、结构-功能可调，在废水处理等污染控制领域有广阔的应用前景。有机膨润土合成-吸附一体化工艺使膨润土大规模用于废水处理工程成为可能，但常见的有机膨润土对水中亲水性芳香类化合物去除效果较差，导致一体化工艺对废水的COD去除效率相对较低，通常要与生化处理等工艺联合才能使废水达标排放。因此有必要调控有机膨润土的结构，提高其吸附亲水性芳香类化合物的能力。近年来有机膨润土的吸附性能与结构特征之间的关系研究引起关注，但仅限于层间的有机相，对层间潜在的吸附点位硅氧烷表面的调控及分子作用机制研究几乎为空白。因此，同时调控有机膨润土层间的有机相和硅氧烷表面的结构特征、提高其吸附亲水性芳香类污染物的能力，是实现有机膨润土大规模废水处理工程应用亟需进一步解决的科学与技术难题。本文从有机膨润土与吸附质之间分子作用的角度探讨了有机膨润土的结构-性能关系，重点研究了有机膨润土硅氧烷表面纳米位点的吸附特征和机理；利用线性溶剂化能关系（LSER）模型定量解析了长碳链有机膨润土水相吸附中的各种物理作用力，考察了有机物性质差异对其在长碳链有机膨润土上吸附性能的影响；并根据亲水性芳香类污染物的特点（含有芳环结构），在有机膨润土的结构中引入芳环基团，利用芳环间的π-π作用增强有机膨润土吸附亲水性芳香类污染物的能力，试图为深入揭示有机膨润土的结构-效应关系和去除废水中亲水性芳香性有机物提供理论依据和技术支撑。本论文取得了以下有价值的研究结果：（1）揭示了膨润土内、外硅氧烷表面的吸附特性及机制。膨润土层间硅氧烷表面极性较弱，而外硅氧烷表面极性较强。膨润土层间位阻效应和芳环效应共同影响层间硅氧烷表面对有机物的吸附。增加层间硅氧烷表面的暴露面积和降低膨润土片层的聚集度可降低层间位阻，从而使有机膨润土吸附有机物的能力增强十至百倍。芳环与硅氧烷表面间的相互作用以及芳环与芳环之间的相互作用增强了芳香类化合物在层间硅氧烷表面上的吸附。由于位阻效应和缺少芳环效应，脂肪类化合物在层间硅氧烷表面上的吸附较弱且很快达到饱和。（2）采用用线性溶剂化能关系（LSER）模型分析了CTMA-膨润土的水相吸附机制，定量解析了各吸附作用力的相对贡献。利用LSER理论对16种有机物水相吸附的固-液分配系数（K_d）进行多元线性回归，得到其LSER模型为：log K_d^cal=-0．464+1．694R₂+2．277V_x-0．435π₂^H+0．591∑α₂^H-1．532∑β₂^H。LSER方程各项系数的显著性分析表明：空穴弥散作用、π-／n-电子对作用、极化／偶极作用、氢键酸作用和氢键碱作用对吸附均有影响。其中空穴弥散和π-／n-电子对作用占主导地位，极化／偶极作用和氢键碱作用抑制吸附。各吸附作用力的相对贡献大小顺序为：空穴弥散作用＞π-／n-电子对作用＞氢键酸作用，而π-／n-电子对作用是产生化合物间吸附性能差异的主要原因。采用核磁共振技术证实有机物与有机阳离子之间π-／n-电子对作用的存在，并揭示该作用的实质为吸附质的大π体系与阳离子端基之间的电子授-受作用。（3）初步探明了有机膨润土层间微环境对π-π作用的影响，并开发了高效去除亲水性芳香化合物的BTMA-低电荷膨润土。在短碳链有机膨润土体系中，芳环间π-π作用受膨润土层间位阻效应的影响；在长碳链有机膨润土体系中，π-π相互作用不受层间位阻效应影响。利用π-π作用和硅氧烷表面疏水作用的原理开发了BTMA-低电荷膨润土，在土水比为5：1（g／L）时，其对苯酚、苯胺和甲苯（20mg／L）的去除率分别达83．3％、89．2％和97．3％，高于常见的有机膨润土，有望解决常见有机膨润土难以高效去除亲水性芳香类污染物的难题。估算了π-π作用和硅氧烷表面疏水作用对BTMA-低电荷膨润土总吸附的相对贡献率，其中芳环间π-π作用的贡献率占90％以上。更多还原

【Abstract】 Organobentonites have many potential applications in environmental protectionbecause of their excellent sorption capacities toward hydrophobic organic pollutants.Some problems need to be further resolved before organobentonite can be widelyused in wastewater treatment,such as improving their sorption capacities especiallyfor water soluble organic contaminants and reducing their costs.To resolve theseproblems,it is necessary to understand the correlation of structural characteristics andsorption capacities of organobentonites.In this dissertation,adsorption characteristicsand mechanisms of siloxane surfaces of bentonites were investigated.And aqueoussorption of organic contaminants to a typical organobentonite was characterized usingLinear Solvation Energy Relationship （LSER） approach.A unique organobentonitewith great sorption capacity toward water soluble aromatic contaminants wasprepared.The main original conclusions of this work are as follows:（1） Adsorption mechanisms of organic comtaminants on the siloxane surfaces ofTMA⁺-bentonites are proposed.Reduction of the layer charge and saturation ofbentonite interlayers with TMA⁺ modify the interlayer microenvironments,whichdramatically promote adsorption of NOCs.Specific mechanisms （i.e.,stericrestriction and phenyl-effect） control the adsorption of NOCs onto internal siloxanesurfaces of TMA⁺-bentonites from water.Adsorption mechanism on the interlayer ofTMA⁺-bentonites varies with solute-loading,from polarity-selective toaromaticity-preferable.Significant contribution of phenyl-effect between adsorbedsolutes to aromatics adsorption on TMA-bentonites is found.Solvent polarity effecton the aggregation of TMA⁺-bentonites and aniline adsorption demonstrated that theexternal siloxane surfaces （generally being omitted） are actually exploited to favoradsorption in nonpolar solvent.（2） Sorption mechanism of organic contaminants onto a typical organobentonite（a bentonite modified by cetyltrimethylammonium （CTMA⁺）） from water wascharacterized using a linear solvation energy relationship （LSER） model.The fitted LSER equation:logK_d^cal=-0.464+1.694R₂+2.277V_x-0.435π₂^H+0.591∑α₂^H-1.532∑β₂^H wasobtained by a multiple regression of the partition coefficients of 16 probe solutesagainst the solvation parameter of the solutes.The coefficients of the LSER equationshow that the sorption of organic solutes onto CTMA-bentonite is dominated byπ-/n-electron pair donor-accepter interaction,cavity/dispersion interactions andhydrogen-bond donor effect.The influence of the properties of organic compounds ontheir sorption onto CTMA-bentonite is recognized to be dominated by theπ-/n-electron pair donor-accepter interaction.This conclusion was also evidenced by¹H-NMR.The greater chemical shift change of CTMA⁺ with 1-nitroaniline thannitrobenzene,1-naphtylamine than N,N-dimethylaniline and aniline thancyclohexanone in ¹H-NMR spectroscopy demonstrated the significant role ofπ-/n-electron interaction in organic contaminants sorption onto CTMA-bentonite.（3） A unique organobentonite （65BTMA） was synthesized by intercalatingbenzyltrimethylammonium cation （BTMA⁺） into the interlayer of a reduced-chargebentonite with cation exchange capacity （CEC） of 65 cmol/kg.Phenol,aniline andtoluene were used as model compounds of water soluble aromatic contaminants.Theremoval efficiencies by 65BTMA were achieved at 83.3%,89.2% and 97.3%respectively,at the initial concentration of 20 mg/L.To 65BTMA,sorptionmagnitudes of aromatic contaminants were much greater than that of aliphaticcompounds with similar size;and dramatically higher than those to otherorganobentonites at low pollutant concentrations.These observations revealed thatthe strong phenyls interactions contributed significantly to sorb the aqueous solublearomatic contaminants to 65BTMA （＞90%）,and which favored to design uniquelypowerful sorbents.更多还原